A late handover scenario, an early handover scenario and an incorrect cell handover scenario resulting from improper setting of handover parameters are defined in a 3GPP (the 3rd generation partnership project, The 3rd Generation Partnership Project) R10 protocol.
Wherein, late handover is as follows: a user equipment (UE, User Equipment) encounters radio link failure (RLF, Radio link failure) in a source cell before initiating a handover or when a handover is ongoing, and then, the UE initiates a radio resource control (RRC, Radio Resource Control) reconstruction in a non-source cell. The reconstruction may succeed or fail, in order to enable a source base station to identify such abnormal handover as late handover, a reconstructed target base station will send an RLF indication (indication) message to the source base station in which the RLF encountered, for enabling the source base station to judge, count and adjust the handover parameters when a subsequent regulation and optimization cycle is up, so as to achieve the purpose of reducing or even avoiding the occurrence of such abnormal handover. Early handover is as follows: the UE encounters the RLF in a short period after successful handover from the source cell to a target cell, and then, the UE initiates the RRC reconstruction in the source cell. Incorrect cell handover is as follows: the UE encounters the RLF in a short period after successful handover from the source cell to the target cell, and then, the UE also initiates the RRC reconstruction in a non-source cell and a non-target cell.
For optimization, it is defined in the 3GPP R10 that, when the UE undergoes handover failure (HOF, Handover failure) or RLF, the UE records some relevant information prior to RLF or HOF, e.g., information of the source cell and target cell subjected to RLF and HOF, or the like, these information is contained in an RLF report (report) with standard definition, when the UE records the RLF report, the UE may report the RLF report to a reconstructed or newly constructed target base station during RRC reconstruction or new RRC construction, and the base station sends an RLF indication (indication) message containing the RLF report to the base station to which the affected source cell belongs, so that the base station to which the source cell belongs may identify, count and optimize relevant scenarios based on the RLF report.
A mobility robustness optimization (MRO, Mobility Robustness Optimization) scenario mainly includes intra-frequency, inter-frequency and inter-system scenarios in a system. At present, the base station could not implement relevant optimization in some scenarios based on the RLF report with existing standard definition.